This theory holds that if the commissioners eventually conclude that the casino end of banks should be separated from the utility end, the chancellor, George Osborne, will simply ignore them. He would not want to risk HSBC hot-footing it to Hong Kong or Bob Diamond taking Barclays to New York.

If the commissioners conclude that splitting is undesirable or impossible, then Cable's big idea would have been examined and found wanting; the business secretary would have to pipe down and stop treading on the Treasury's toes.

Now, the sketch above clearly has some truth to it. The banking commission represents the end of the road for the utility-versus-casino debate. Next September, when its report is published, is decision time.

Would Osborne really issue a blunt order to Barclays and HSBC to split themselves up? It seems unlikely. Even after the calamities, the bailouts and the embarrassing queues outside Northern Rock, it is hard-wired into political thinking that banking is a British sport. Osborne would not wish to be left with a couple of dodgy full-backs – Royal Bank of Scotland and Lloyds – while waiting to see if the more dynamic Barclays and HSBC put in transfer requests.

True, not every country wants to host a bank with an intimidating balance sheet and an inflated sense of its own importance, but nor are those threats of emigration absurd: 20 years ago, HSBC was not based in the UK.

So do these hard political realities make the banking commission a waste of time?

Actually, no: there is more to this debate than whether retail banks and investment banks should exist under the same roof.

When Cable admitted 10 days ago that the big banks might avoid being split up on "crude" lines, he invited scorn. Labour former chancellor Alistair Darling said, fairly, that he detected "the screeching of brakes, shortly before the execution of a U-turn". But Cable's point that more "subtle" methods are available – such as erecting "firewalls" between parts of the bank – is hardly an admission of despair about the problem of banks that are too big to fail.

The commissioners might say that the investment banking activities of universal banks should be supported by truly colossal sums of capital. That would not satisfy hard-line splitters, who maintain that bankers always run rings around regulators eventually, but this is an area where the commissioners might seek consensus. And, if we know anything about the commission, it's that its members will try to find a report that they can all put their names to.

Martin Taylor, the former Barclays chief executive, will be an interesting swing voter on the panel – at least, to judge by his testimony to the Which? Future of Banking Commission. Taylor said he thought the universal banking model "has proved to be very dangerous" but also said that universal banks are very difficult to dismantle.

He doesn't place much faith in the ability of regulators to outwit determined traders: "Traffic wardens don't break up drug cartels," he remarked dryly. He also said it would just be "tough" if there were reforms the banks didn't like.

The banking commission might also copy some of the reforms proposed by that Which? body (of which Clare Spottiswoode, another member of the new commission, was also a panellist). They included forcing banks to make public their "living wills" – the documents intended to show how the core deposit, lending and payments functions can be ringfenced in a crisis.

Another big idea was to split investment advice from corporate advice. That may sound tame on paper but would represent real change in the way investment banks operate.

Then there is an enormous question of whether the likes of Lloyds, with about a third of the UK market for current accounts, have an unfair advantage. The issue of competition gets less publicity, but it's hardly a trifling matter. It could open the door to a full inquiry that was denied at the time of Lloyds' takeover of HBOS.

The point is that trying to second-guess the conclusions of the banking commission is pointless at this stage. Yes, we can probably all agree that a Tory-led government, despite the encouragement of the Bank of England, would not allow a full break-up of universal banks. But the interesting part is the alternative solutions. And they might just surprise the sceptics.